Due to some superior physical properties of AuSn alloy, such as low melting point and good ductility, AuSn alloy has been applied in semiconductor and other industries for years, and gradually becomes one of the preferred materials for soldering in optoelectronic device package. The melting point of AuSn alloy is below 280° C., which benefits for solder bond in optoelectronic device package application. But during laser dicing of the optoelectronic device, the operating temperature of laser is often higher than 1000° C., which conflicts with the low melting point and the good ductility of AuSn alloy, and a volcano defect 17s shown in FIG. 1 and FIG. 2 forms on AuSn alloy 16 when AuSn alloy 16 is formed on an optoelectronic device 10 after laser dicing. The volcano defect 17s makes the optoelectronic device 10 not being able to be mounted on a package board with good reliability.